Arrived on site to perform furnace maintenance on 23 year old Lennox furnace. Cycled system for heat. Verified proper heating sequence of operations. Temperature rise across heat exchanger is within range. Ran system through 20 point inspection checklist. Cleaned heating and blower compartment. Wiped down the exterior of the furnace. Went over findings and recommendations with homeowner. Spoke on the topic of system replacement, homeowner currently does not want to put any money into the existing units and is waiting to be ready form replacement. Discussed different type of system options and which one would be most effective for the home and how they use it. Current systems are just single stage units with 2 zones, which is not ideal. Cycled system, system is operational upon departure.